Compressor capacity control



y 24, 1956 K. M. GERTEIS 87 COMPRESSOR CAPACITY CONTROL I Filed Oct. 2, 1952 INVENTOR.

m-m BY Ma 06 United States atent- O COMPRESSOR CAPACITY CONTROL Karl M. Gerteis, Syracuse, N. Y., assignor to Carrier Corporation, Syracuse, N. Y., a corporation of Betaware Application October 2, 1952, Serial No. 312,713

5 Claims. (Cl. 230-22) This invention relates to apparatus for controlling the capacity of a reciprocating compressor and more particularly to apparatus for lay-passing discharge gas from the cylinder head to the compressor suction manifold when full capacity is not required or desired.

One of the disadvantages of the prior ant capacity controls has been the added equipment necessary tobe installed outside of the compressor.. Such added equipment has resulted in greater installation expense and a higher cost of maintenance.

The present invention eliminates these disadvantages by providing a by-passing capacity control element that is a part of the compressor itself.

The chief object of the present invention is to provide a compact, self-contained cylinder by-pass [type capacity control arrangement for loading or unloading tone or more cylinders of a compressor.

An object of the present invention is to provide an apparatus that will reduce the starting torque requirements of the compressor.

Another object of the present invention is to provide an apparatus which will permit separate unloading of the cylinders of a compressor when desired.

A further object of the invention is to provide an apparatus for capacity control of a compressor that is more economical than the present controls. Other objects of the invention will be readily perceived from thefollowing description.

This invention relates to a power element for use in a reciprocating compressor, the power element including a sleeve, a piston in the sleeve adapted to close an opening between the cylinder head and the suction manifoldf the compressor, and means for applying pressure to the piston to move the piston from a first position to a second position to close the opening, said means applying discharge pressure at predetermined intervals to move the piston from the first position to the second position and applying suction pressure at other predetermined intervals to move the piston from the second position to first position to open the opening. 7

The attached drawing illustrates a preferred embodiment of my invention, in which Figure lnis a view partly in section and partly in elevation of a portion of a compressor cylinder including the apparatus of the present invention;

Figure 2 is ase'ctional view of the 'oil pilot valve in loaded position connected to the power element; and

' Figure 3 is a sectional view of the-oil pilot valve in unloaded position.

Referring :to the drawing, there disclosed a compressor 2 including the capacity control of the present invention. The compressor 2 includes a cylinder head 3 formed in the upper portion of the compressor 2. A valve plate 4 is placed between cylinder head -3 and -a cylinder 5. It will be understood a plurality of cylinders may be employed if desired. This cylinder communicates with the cylinder head through openings 6 in the valve plate 4. A' piston 7 is disposed fwithiin the cylinder 2 and moves therein. This piston has two chambers 8, longitudinally disposed therein, which communicate with suction ports 9 disposed in the wall of the cylinder 5.

A suction valve 11 is positioned on the top of the piston 7 to close ports 12 in the top of the piston. A discharge valve 13 is disposed in the cylinder head 3 over the openings 6 in the valve plate and controls flow through the openings. A second opening -14 is provided in the valve plate 4. This opening communicates with a discharge manifold 15, which leads to the condenser of the usual refrigeration system. This second opening 14 is controlled by check valve 16 which permits flow only from the cylinder head to the discharge manifold.

A third opening '22 is provided in the valve plate 4 and permits flow from the cylinder head .3 to the suction manifold 23. The suction manifold is disposedabout the cylinder *5. It will be understood that if a plurality of cylinders are employed, the suction manifold will communicate with all the cylinders.

This third opening 22 is controlled by a power element 26, which includes a piston 27 movable in a sleeve 28. A member 29 is provided to seal the open end of the piston and sleeve. .A pressure connection 30 leads through the member 29 to permit pressure to :act on the piston 27. This piston rests on a seat 31 provided around the opening 22.

The pressure connection 30 leads from the power element 26, to a three-way valve 35. Preferably, a threeway solenoid valve is employed. However, a manually controlled valve'or other similar means may .be used. A line 36 connects the three-way valve 35. with an 'oil pilot valve 37.

The oil pil'ot valve 37 includes a casing 34 that has an oil pressure connection 38. Oil is supplied from the compressor lubrication system oil pump to the connection to act against a piston 39 in the valve. This piston has a protuberance 40 which extends into a chamber 41. This chamber is in communication with the suction pressure of the system. Abal'l 42 is'positioned in the chamher on top of the protuberance 40. This chamber 41 extends into an elongated passage 43 in which is positioned a'rod 44' which rests on ball 42.

An opening 45 in passage 43 connects the passage to line 36. A second chamber 46 is provided at the opposite end iofthe passage 43. A second ball 47 is disposed in the second chamber. This second chamber communicates with the discharge pressure of the system. A valve seat '48is placed-in the chamber 41 above the ball 42 and surrounds passage 4'3. A valve seat 49 is located in the second chamber below the second ball 47 and surrounds the opposite end of passage 43. Disposed above the second ball 47 is a spring 50, which tendsto force the ball 47 onto the valve seat 49.

Suction pressure will exist in line 6'6 when chamber the second ball 47 occurs when oil pressure is suppliedto oil pressure'connection 38. This, of course, is when the motor is running at full speed.

While the oil pilot valve is the preferred manner of regulating pressure to the pressure connection 30, this valve can be eliminated if oilwere supplied to the pressure connection rather than'the discharge pressure ofthe gas. However, if this type of operation is used, the oil might tend to leak past the piston 27 into the gas of the cylinder head and such is not desired in some refrigeration applications.

Control of'the power element may be accomplished by other suitable means. The essential requirement is that pressure applied against the power element is varied in response to a changein suction pressure or in the temperature of the fluid being cooled.

.ing of the cylinder.

Considering the operation of the apparatus, the gas enters the cylinder 5 through the suction ports 9. On

downward movement of the piston 7, the suction valve 11 opens to let the gas enter the cylinder above the piston.

,Upon upward movement of the piston, the suction valve closes and the gas is compressed to a predetermined pressure that is sufficient to overcome the discharge valve .13. At this time, the gas passes through the openings 6 into the cylinder head 3. During normal loaded operation this gas passes through the second opening 14 into the discharge manifold to the refrigeration system. It will be understood that the check valve 16 will be overcome by the pressure of the gas to permit the gas to flow through the opening during loaded operation.

During starting of the compressor, it isdesirable that one or more of the cylinders of the compressor be in unloaded condition; this is accomplished by the power element 26. The piston 27 of the power element has a portion of its area extending beyond the seat 31. This area of piston 27 beyond the seat is, at all times, exposed to discharge pressure under the cylinder head 3. The area of the piston that iswithin the seat 31 is exposed to the. suction pressure existing within the suction manifold.

These two areas are equal to the inner area of the piston,

which is subject to pressure through pressure connection 30. a

The pressure applied to the piston through 1 the pressure connection 30 may be either suction pressure or discharge pressure. When the compressor starts and the oil pressure is starting to build up, the position of the elements in the oil pilot valve 37 is such that suctionpressure will exist in lines 36 and pressure connection 30. If the compressor is running and the oil pressure is built up, the position of the elements in the oil pilot valve 37 will be such that discharge pressure exists in line 36 and pressure connection 30. Thereafter, if it is desired for suction pressure to exist in the pressure connection 30,, the three-way valve 35 must be utilized to block line 36 and open line 51, which is in communica tion with the suction pressure of the system.

The position of the piston 27 in power element 26 depends on Whether suction pressure or discharge pressure is applied through pressure connection 30. Therefore, if suction pressure is applied through the pressure connection, the forces resultingfrom the pressure acting against the inner area of the piston will be less than the forces acting against the outer area of the poston. The forces acting against the outer area of the piston, of course, are produced by the discharge pressure applied against the exterior area outside the seat and the suction pressure applied against the exterior area inside the seat. As a result the piston will be caused to move away from the seat to uncover the third opening 22 permitting the gas in the cylinder head to be by-passed to the suction 'manifold. At this time, the check valve 16 serves the function of preventing any of the gas in the discharge 4 manifold from flowing back through the second opening 14 into the cylinder head 3.

If the inner area of the piston is subject to discharge pressure through the pressure connection, the forces applied against the inner area from this pressure will be greater than the combined forces applied against the outer area. Therefore, the piston will be caused to contact the seat and close the third opening. As a result, the gas in the cylinder head will build up a pressure slightly exceeding the pressure in the discharge manifold and thus cause the check valve to open and permit the gas to flow into the discharge manifold. V

The operation of the oil pilot valve is dependent upon the oil pressure of the compressor. When the compressor is running and the oil pressure is built up, the protuberance 40 extends into the chamber 41 a maximum distance since the oil entering the oil pressure connection 38 causes the piston 39 to move to its uppermost position. This causes the ball 42 to sit against valve seat 48. The ball 42, through rod 44, moves the second ball 47 upward to overcome the force of spring 50 and lift the ball off of the valve seat 49. In this relation, the power element is subject to discharge pressure since pressure connection 30 is in communication with opening 45 by means of line 36. I Thus, piston 27 of power element 26 is forced onto the seat 31 and third opening 22 in the valve plate is closed. The gas from the cylinder head 3 then flows to the discharge manifold, since the pressure of the gas is of sufficient force to open check valve 16, which blocks opening 14.-

When the compressor is starting and the oil pressure .is building up, the piston 39 is at its lowermost position since it is subject to no pressure from the oil pressure connection 38. The protuberance 40 barely enters the chamber 41 and the ball 42 moves down from its valve seat 48. This downward movement of the ball 42 causes the rod 44 to move downward and enables the spring 50 to force the ball 47 onto its valve seat 49. With the parts of the oil pilot valve in this position, suction pressure is applied to the power element through chamber 41, passage 43, and opening 45 to line 36 and the pressure connection 30. With the suction pressure thus being applied through the pressure connection 30, the piston 27 of the power element 26 is forced upwardly and the third opening 22 is'uncovered. This permits the gas in the cylinder head to be by-passed during starting operation of the compressor.

After the compressor is in operation, to permit unloading of some of the compressor cylinders, another control may be provided to by-pass the gas. This is accomplished by the three-way valve 35. This valve normally permits flow through line 36 to pressure connection 30. When it is desired to by-pass the gas after the compressor has started, this valve blocks line 36 and connects line 51, which is in communication with the suction pressure of the system, to pressure connection 30. Therefore, it will be understood that when the line 36 is closed and line 51 is open the piston 27 of power element 26 will be caused to move upward and uncover the opening 22 to permit the gas to be by-passed. 'Preferably a three-way solenoid valve is employed; however, a manually controlled valve or other suitable means may be used.

The present invention provides a simplified capacity control system in that it places the by-pass structure inside of the compressor. This apparatus provides both control of starting operation and control of the capacity of the compressor during operation.

While I have described a preferred embodiment of my invention, it will be understood that my invention is not limited thereto since it may be otherwise embodied within the scope of the following claims.

I claim: i

- 1. In combination with a reciprocating compressor including a cylinder head, a suction manifold, a member separating the head from the manifold, said member having an opening therein, a seat on said member and disposed about the opening, a power element which includes a sleeve and a piston in said sleeve adapted to rest on said seat to close said opening, said piston being of such dimensions as to overlie the seat, the exterior of said piston being subject at all times to suction pressure acting on the exterior area inside the seat and discharge pressure acting on the exterior area outside the seat, means to apply pressure to the interior of the piston, said means applying discharge pressure to the interior of the piston at predetermined intervals to overcome the combined forces acting on the exterior of the piston to move the piston to close the opening, and said means applying suction pressure to the interior of the piston at other predetermined intervals so that the combined forces acting on the exterior of the piston will be greater than the forces acting on the interior of the piston to permit movement of the piston away from the opening.

2. In a reciprocating compressor, the combination of a cylinder having a compression chamber, a piston in said cylinder, said cylinder having suction ports therein, a suction manifold disposed about said cylinder, a suction valve preventing flow of refrigerant between the compression chamber and the suction manifold, a cylinder head above the piston, a discharge valve regulating flow from said compression chamber to said head, a discharge manifold, a check valve controlling the gaseous fiow from said head to the discharge manifold, and a power element closing an opening between said head and said suction manifold, said power element being adapted to by-pass the gas from said head to said suction manifold under predetermined conditions, said power element operable in response to relative changes in the suction and discharge pressure.

3. In combination with a refrigeration system including an evaporator, a condenser, and expansion means, a compressor including a cylinder having a compression chamber, a piston in said cylinder, said cylinder having suction ports therein, a suction manifold disposed about said cylinder, a suction valve preventing flow of refrigerant between the compression chamber and the suction manifold, a cylinder head, a discharge valve regulating flow from said compression chamber to said head, a discharge manifold leading from the cylinder head to the condenser, a member separating said head and said discharge manifold and having an opening therein, a check valve governing said opening to permit the flow of gas from said discharge manifold to said head, said member having a second opening therein that connects said head and said suction manifold, a seat surrounding said second opening, and a piston adapted to sit on said seat and close said second opening, application of discharge pressure of the system to said piston moving said piston to close said second opening, and application'of suction pressure of the system to said piston permitting movement of the piston away from said second opening.

4. Apparatus according to claim 3 in which the cornpressor piston is hollow and the interior of the piston is in communication with the suction ports, said piston having an opening in the top thereof, and said suction valve being located on top of the piston to regulate the opening.

5. in combination with a refrigeration system, a reciprocating compressor comprising a plurality of cylinders with each cylinder having a compression chamber, a piston in each cylinder, each cylinder having suction ports therein and a suction manifold connected to the ports of the cylinders, a suction valve preventing flow of refrigerant between the compression chamber and the suction manifold, a cylinder head, a discharge valve regulating flow from each piston to each head, at least one of said cylinders having a by-pass means to circulate the gas from the discharge valve to the suction ports without passing through the remainder of the refrigeration system, each cylinder with a by-pass means having a check valve in its head to prevent back flow from the system, said by-pass means including a power element adapted to control flow from the discharge valve to the suction ports, said power element including a sleeve and a piston therein and preventing flow from the head to the manifold when the interior of the piston is exposed to discharge pressure and permitting flow when the interior of the piston is exposed to suction pressure.

References Cited in the file of this patent UNITED STATES PATENTS 1,910,000 Buehler May 23, 1933 1,911,105 Buehler May 23, 1933 2,036,846 Aldinger Apr, 7, 1936 2,036,847 Aldinger Apr. 7, 1936 2,110,720 Crittenden Mar. 8, 1938 2,274,337 Ritter Feb. 24, 1942 2,350,537 Scott June 6, 1944 

